SEOUL - North Korea sent a rare letter of protest to the U.S. House of Representatives on Friday warning that a new package of tougher sanctions would only spur its development of nuclear weapons, North Korea's state media reported.

The protest was lodged by the recently revived Foreign Affairs Committee of North Korea's Supreme People's Assembly, which said the House of Representatives was "obsessed" with a sense of disapproval and warned it of dire consequences.

"The U.S. House of Representatives should think twice," the committee said in its letter, a copy of which was published by the KCNA state news agency.

Tension has been high for weeks over North Korea's nuclear and missile development and fears it will conduct a sixth nuclear test or test-launch another ballistic missile in defiance of U.N. Security Council resolutions.

The House of Representatives overwhelmingly approved legislation this month to tighten sanctions by targeting North Korea's shipping industry and companies that do business it.

The U.S. legislation was intended to cut off supplies of cash that help fund North Korea's nuclear programme, and increase pressure to stop human rights abuses such as the use of slave labour, the bill's sponsor said.

The North's committee said it would fail.

"As the U.S. House of Representatives enacts more and more of these reckless hostile laws, the DPRK's efforts to strengthen nuclear deterrents will gather greater pace, beyond anyone's imagination," the committee said, referring to North Korea by the initials of its official name, the Democratic People's Republic of Korea.

Last month, North Korea reconvened the Foreign Affairs Committee, which was abolished in the late 1990s, in what analysts saw as an attempt to improve relations with the outside world amid its deepening isolation.

The committee is chaired by Ri Su Yong, a close aide to leader Kim Jong Un and a career diplomat.